Significant Event Report for Week Ending 7/2/2004

Cassini Significant Event Report

For Week Ending 07/02/04

The most recent spacecraft telemetry was acquired from the Canberra tracking station on Wednesday, June 30th. The Cassini spacecraft is in an excellent state of health and is operating normally. Information on the present position and speed of the Cassini spacecraft may be found on the "Present Position" web page located at http://saturn.jpl.nasa.gov/operations/present-position.cfm .

During the quiet period leading up to Saturn Orbit Insertion (SOI), members of the Spacecraft Operations Office (SCO) monitored spacecraft real-time telemetry on a continuous basis. All operations were nominal and per predict. Monitoring continued through the pre-SOI critical commanding period and up until the swap to low gain antenna-1 was commanded. From that time until a scheduled "call home" after the burn, spacecraft performance was monitored via the Radio Science Receivers (RSR).

After the antenna swap, the spacecraft was oriented so that the high gain antenna (HGA) could be used as a shield, protecting Cassini from potential dust impacts as the spacecraft performed its ascending ring plane crossing through the gap between the F and G rings.

Traveling at a speed of over 20 km/sec kilometers per second, the spacecraft was reoriented for a 96-minute main engine burn. This slowed the spacecraft by 626 meters per second and allowed it to be captured by the gravitational pull of Saturn. During this time, five science instruments remained on collecting data that will be unique in the lifetime of the Cassini mission. Never again will Cassini travel as close to Saturn as it did at 9:03 p.m. PDT when it reached closest approach of 19,980 kilometers from the cloud tops.

After completion of the burn, Cassini turned so that the HGA was aimed back toward Earth for a 20-second burst of telemetry. This "call home" confirmed for the flight team that the spacecraft was operating normally. Cassini then turned away and began execution of a science observation sequence. Science obtained at this time was key, in that the spacecraft was within 15000 kilometers from Saturn's main rings, ten times closer to the rings than at any other point in the mission, and in a region of space that had not been previously observed.

Unique post-SOI science activities included: measurement of the strength and direction of the magnetic field by the Cassini Magnetometer (MAG), ring observations by the Optical Remote Sensing Instruments, measurement of the very sparse neutral molecules in Saturn's atmosphere by the Ion and Neutral Mass Spectrometer (INMS), measurement of the charged particles by the Cassini Plasma Spectrometer (CAPS), and detection of radio emissions emitted by lightning strokes in Saturn's atmosphere by the Radio and Plasma Wave Science instrument (RPWS).

Science data playback began in the early hours of Thursday July 1. Images are now available for viewing at: http://saturn.jpl.nasa.gov.

A very significant event to occur immediately after SOI was the jettison of the INMS cover. The cover was left on the instrument since launch until after the SOI burn was complete. This was to prevent potential contamination of the instrument by exhaust material from the long burn. Prior to jettison, INMS was filled with argon to insulate and protect the interior walls. Team members were able to confirm a successful jettison when sensors noted the depletion of the argon gas. INMS was powered up at 3:39 SCET and is now taking data for the first time in the mission.

ACS analysis of official port #1 products from Science Operations Plan (SOP) implementation of tour sequences S31/S32 has been completed. The teams are working off issues in preparation for preliminary port #2.

Due to SOI activities, the Project Briefing and Waiver Disposition meeting for the SOP Update process of S04 was canceled. The handoff product will be generated and delivered to the sequencing team next week.

The Aftermarket decision meeting for S06 was canceled since the number of changes requested for this sequence was minimal.

System Engineering hosted a Phoebe lessons learned discussion this week. The Phoebe flyby was the first time an IVP update was required. This activity will be performed numerous times throughout the mission so the capturing of information now will assist in future operations. Items on the agenda included discussion of target motion compensation and live update, planning and testing for the flyby beginning with the SOP Update process and including operations readiness tests that were performed for Phoebe, overview and recommendations for an end-to-end "once the dust settles" assessment of the process, general lessons learned, and follow ups.

As expected, quite a number of articles and interviews have appeared on Cassini's Saturn Orbit Insertion in the last 24 to 48 hours. A sample of titles and links to the articles appear below:

NPR's Richard Harris filed a story on the Cassini SOI (Morning Edition on 7/1/2004). You can hear the story in its entirety (~4m 7s) at the following link:

http://www.npr.org/features/feature.php?wfId=3063001

Additional information about Cassini-Huygens is online at http://saturn.jpl.nasa.gov.

Cassini will begin orbiting Saturn on July 1, 2004, and release its piggybacked Huygens probe about six months later for descent through the thick atmosphere of the moon Titan. Cassini-Huygens is a cooperative mission of NASA, the European Space Agency and the Italian Space Agency. JPL, a division of the California Institute of Technology in Pasadena, manages the mission for NASA's Office of Space Science, Washington, D.C.